Cigarette smoke (CS) is the primary cause of COPD, the fourth leading cause of death in the US. CS-induced oxidant stress causes endothelial cell (EC) apoptosis, and there is growing evidence that apoptosis of alveolar wall cells plays a role in the development of emphysema. The overall objective of this proposal is to understand mechanisms of CS-induced lung EC apoptosis and emphysema. Our previous studies on carboxylmethylation of small GTPases indicated that inhibition of RhoA GTPase activity causes focal adhesion complex (FAC) disruption and lung EC apoptosis. We present preliminary data indicating that CS extract (CSE) disrupts FAC via oxidative stress, causes EC apoptosis, and decreases RhoA activity. Aim 1: We will determine if oxidant- mediated RhoA inactivation causes CSE-induced loss of FAC and apoptosis of pulmonary EC. Our previous studies also demonstrated that EC apoptosis occurs despite activation of the unfolded protein response (UPR) when ER molecular chaperones are decreased. Our preliminary data indicate that CSE activates a UPR component, eIF2a, which was also activated in emphysematous lungs of mice exposed to CS. Aim 2: We will determine if UPR is first activated upon CSE exposure and ultimately defective after prolonged oxidative stress in pulmonary EC. Autophagy is a protective process, markers of which have been demonstrated in lungs of COPD patients. Our preliminary data demonstrate increased expression of autophagy markers in lung endothelial cells exposed to CSE and in lungs of mice exposed to CS. Aim 3: We will determine if autophagy is activated upon CSE exposure and ultimately defective after prolonged oxidative stress in pulmonary EC. The proposed studies will enhance understanding of the pathogenesis of emphysema and may result in develop of new therapeutic approaches to this devastating disease. PUBLIC HEALTH RELEVANCE: Chronic Obstructive Pulmonary Disease (COPD) is the fourth most common diagnosis of hospitalized veterans, accounting for about 33% of all primary or secondary discharge diagnoses. Tobacco use, the most common cause of COPD, is also very common among veterans with a prevalence of 34% (compared to 22% for civilians). Thus, tobacco-induced COPD is a very costly cause of morbidity among veterans in terms of both healthcare costs and suffering. Furthermore, COPD is an important co-morbidity for other common p0roblems among veterans, such as lung cancer and atherosclerosis. Thus, it is very important to understand the mechanism of tobacco-induced lung disease. The studies proposed in this application are directly relevant to veterans'health in that these studies will determine the mechanism of injury to the lung vascular endothelium caused by tobacco and the role that this plays in development of COPD. These studies may result in development of more effective treatments for COPD.